I might not remembering the scene right...but dont we see a lot of cars stopped in the emp tunnel scene ? There's a scene of a guy even trying to escape by running away from his bike and some cops grab him. Before we see exactly the motorcycle guy unable to keep escaping with the hostage. He even stops , and the guy escapes. Then after it , Batman fails shooting the other one. So i saw the emp clearly interfering with the engines (which i suppose would be the result) of the bikes. Even the sound of the scene is clear , with motor engines trying to start again.